Anderson/add new forwarder contract (#440)

* add minimal forwarder

* rename test forwarder contract

* add tests for the new forwarder

* add forwarder test

* rename test

* fix comments

* fix comments

* remove responseForwarder

contracts/Forwarder.sol

@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: LGPL-3.0-only
+pragma solidity 0.6.12;
+pragma experimental ABIEncoderV2;
+
+import "@openzeppelin/contracts/cryptography/ECDSA.sol";
+import "@openzeppelin/contracts/drafts/EIP712.sol";
+
+/**
+    @notice This contract refers to Openzeppelin's MinimalForwarder contract.
+ */
+contract Forwarder is EIP712 {
+    using ECDSA for bytes32;
+
+    struct ForwardRequest {
+        address from;
+        address to;
+        uint256 value;
+        uint256 gas;
+        uint256 nonce;
+        bytes data;
+    }
+
+    bytes32 private constant _TYPEHASH =
+        keccak256("ForwardRequest(address from,address to,uint256 value,uint256 gas,uint256 nonce,bytes data)");
+
+    mapping(address => uint256) private _nonces;
+
+    constructor() EIP712("Forwarder", "0.0.1") public {}
+
+    function getNonce(address from) public view returns (uint256) {
+        return _nonces[from];
+    }
+
+    function verify(ForwardRequest calldata req, bytes calldata signature) public view returns (bool) {
+        address signer = _hashTypedDataV4(
+            keccak256(abi.encode(_TYPEHASH, req.from, req.to, req.value, req.gas, req.nonce, keccak256(req.data)))
+        ).recover(signature);
+        return _nonces[req.from] == req.nonce && signer == req.from;
+    }
+
+    function execute(ForwardRequest calldata req, bytes calldata signature)
+        public
+        payable
+        returns (bool, bytes memory)
+    {
+        require(verify(req, signature), "MinimalForwarder: signature does not match request");
+        _nonces[req.from] = req.nonce + 1;
+
+        (bool success, bytes memory returndata) = req.to.call{gas: req.gas, value: req.value}(
+            abi.encodePacked(req.data, req.from)
+        );
+
+        assert(gasleft() > req.gas / 63);
+
+        return (success, returndata);
+    }
+}

contracts/TestContracts.sol

@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: LGPL-3.0-only
 pragma solidity 0.6.12;
+pragma experimental ABIEncoderV2;
 
 import "./utils/SafeCast.sol";
 import "./handlers/HandlerHelpers.sol";
@@ -80,10 +81,29 @@ contract HandlerRevert is HandlerHelpers {
     }
 }
 
-contract Forwarder {
+contract TestForwarder {
     function execute(bytes memory data, address to, address sender) external {
         bytes memory callData = abi.encodePacked(data, sender);
         (bool success, ) = to.call(callData);
         require(success, "Relay call failed");
     }
 }
+
+contract TestTarget {
+    uint public calls = 0;
+    uint public gasLeft;
+    bytes public data;
+    bool public burnAllGas;
+    fallback() external payable {
+        gasLeft = gasleft();
+        calls++;
+        data = msg.data;
+        if (burnAllGas) {
+            assert(false);
+        }
+    }
+
+    function setBurnAllGas() public {
+        burnAllGas = true;
+    }
+}

package.json

@@ -41,7 +41,9 @@
     "rollup-plugin-typescript2": "^0.30.0",
     "rollup-plugin-node-polyfills": "^0.2.1",
     "rollup-plugin-peer-deps-external": "^2.2.3",
-    "typescript": "^4.2.3"
+    "typescript": "^4.2.3",
+    "eth-sig-util": "^3.0.1",
+    "ethereumjs-wallet": "^1.0.2"
   },
   "peerDependencies": {
     "ethers": ">= 5.0.0"